Recently, the wide employment of information-processing equipment, on which a liquid crystal display for displaying information and a touch panel (called a touch screen, a transparent membrane switch) for inputting information were mounted, began. Most of the touch panels are resistance film type ones. The resistance film type touch panels are fabricated by setting two transparent electrode substrates (a movable electrode substrate and a fixed electrode substrate) having transparent conductive layers formed thereon, respectively, facing each other at a distance of 10 to 100 μm. In order to maintain insulation between the movable electrode substrate and fixed electrode substrate in the absence of external force, dot spacers are usually formed on the electrode surface of the fixed electrode substrate. Due to this construction a touch by a finger or pen on the outside of the movable electrode substrate causes contact between the electrode surfaces of the movable electrode substrate and fixed electrode substrate only at the touched site, thereby resulting in switch and, for example, allowing selection of a menu on the liquid crystal display or input of a drawn figure or written characters.
Such information-processing equipments having touch panel-equipped liquid crystal display are often used in portable form in the case of, for example, camcorders, PDAs (Personal Digital Assistants), smart phones and the like. Because the touch panel-equipped liquid crystal displays of such portable information-processing equipments are generally used outdoors, they are inevitably used under light sources emanating from different directions. Consequently, noise light (reflected light from the touch panel section) also enters the eye simultaneously with the image recognition light (for example, light from the liquid crystal display), thus rendering the display more difficult to distinguish.
Japanese Unexamined Patent Publication HEI No. 5-127822 describes a touch panel which reduces reflected light by a laminated construction of a ¼ wavelength retardation film, a polarizing plate and a nonglare-treated transparent film, in that order on the touch panel section. The touch panel is effective for reducing reflected light from the touch panel section, but coloration of light from the liquid crystal display by the ¼ wavelength retardation film has been a problem.
WO99/66391 discloses a touch panel employing a retardation film having a retardation of 90-200 nm and a photoelastic constant of 5×10−13 cm2/dyne to 65×10−13 cm2/dyne (5-65×10−12 Pa−1), and a pair of transparent conductive substrates. This publication also mentions that the retardation film having a transparent conductive layer formed thereon can be used for the transparent conductive substrate of the touch panel.
However, it has been found that lack of a protective layer on a side opposite to the transparent conductive layer-formed side of the retardation film can sometimes create problems during actual manufacturing, such as scratching of the retardation film during the process of forming the transparent conductive layer or the processes of making up the touch panel, or can lead to insufficient reliability of adhesion when the retardation film is attached to the polarizing plate. However, it has become apparent that when a layer, which performs a function of improving adhesion with the polarizing plate as well as a function of preventing damage during the various making up processes, is formed on the polarizing plate lamination side of the retardation film, red-green stripes become distinguishable due to film thickness deviation of the layer and thus reduce the visibility of the liquid crystal display.
On the other hand, Japanese Unexamined Patent Publication HEI No. 5-50561 discloses a transparent conductive film (transparent conductive laminate) having one side of the film surface roughened to center line average roughness (Ra) in the range of 0.05-5.0 μm and having a transparent conductive layer formed on the other side, as well as a touch panel having a construction employing the transparent conductive film (transparent conductive laminate) as a lower sheet (fixed electrode substrate). When a support sheet is set in contact with the lower sheet for reinforcement of the touch panel, color stripes are produced due to light interference between the lower sheet and the support sheet hitherto, but aforementioned formation of a roughened surface on the lower sheet prevents the light interference-induced color stripes. As a method of forming the roughened surface there is mentioned a method of forming a layer comprising inorganic fine particles or organic fine particles. This method is effective for eliminating red-green stripes, but because center line average roughness is too large, the haze is increased and the visibility of the liquid crystal is thus impaired.